In wireless communications systems, such as those operating in accordance with 3GPP2 CDMA2000-1x EVDV standards or 3GPP UMTS W-CDMA standards, for high-speed data transmission the base station (or NodeB in UMTS terminology) transmits on the forward channel to the mobile terminal (UE [User Equipment] in UMTS terminology) to which the data is directed, a pilot signal (Common Pilot Channel—CPICH for UMTS), a Forward Packet Data Channel (F-PDCH, or High Speed Downlink Shared Control Channel—HS-SCCH for UMTS), and Forward Packet Data Control Channel (F-PDCCH, or High Speed Downlink Shared Channel—HS-DSCH for UMTS). In order for the base station to determine a proper data rate, a modulation scheme, and a transmit power for the F-PDCH and F-PDCCH, it needs to have some measure of how “good” the channel currently is. Accordingly, the mobile terminal provides a measure of channel quality to the base station via a Channel Quality Indicator Channel (CQICH) that is transmitted on the reverse link. In determining what CQI the mobile terminal should transmit back to the base station, the Ec/Nt signal-to-noise ratio (SNR) of the pilot signal received by the mobile terminal from the base station is used by the mobile terminal as an input to a look-up table (LUT), which quantizes that received pilot SNR into 16 possible levels, each of which is represented at a 4-bit CQI word. That CQI, when transmitted by the mobile terminal and received and detected by the base station, is converted at the base station back into its corresponding Ec/Nt pilot SNR, which is then used by the base station to set the downlink power, the modulation scheme, and the rate for the base station's next downlink transmission. Since the received CQI is a measure of the channel condition during a time period that has just passed, the base station may process the determined Ec/Nt to predict a current channel condition.
A received CQI that has been corrupted by noise on the channel and detected in error can have a deleterious effect on the system performance. For example, if the CQI that has been detected from received soft symbol metrics and converted to its corresponding Ec/Nt pilot SNR is indicative of a channel quality that is better than the actual channel quality, then the base station will allocate a higher rate and lower power than is required, which transmission will then have a high probability of not being accurately received by the mobile terminal. As a result, the base station will likely have to retransmit, thereby affecting system latency. On the other hand, if the detected CQI when converted to its corresponding Ec/Nt pilot SNR is indicative of a channel that is worse than the actual channel quality, then the base station will then transmit at a lower data rate and at a higher power level than is required. This higher-than-necessary power level can cause interference on adjacent cells, and the transmission will take longer than is necessary since its data rate will be lower than what it could be for the actual channel conditions. In both cases, it probably would be better to use a previous CQI value that was known to be a “good” representation of the previous channel condition than a CQI that is a “bad” representation of the current channel condition. The prior art, however, provides no way of determining whether a received CQI is a “good” or a “bad” representation of the current channel condition.